The present invention relates generally to an apparatus and method for performing a thermal therapy patient treatment protocol. More particularly, the invention relates to a novel apparatus and method for inducing non-target tissue to generate a heat protective response and then irradiating and/or heating target tissue, such as the prostate gland, for therapeutic purposes.
Thermotherapy treatment is a relatively new method of treating diseased and/or undesirably enlarged human tissues. Hyperthermia treatment is well known in the art, involving the maintaining of a temperature between about 41.5xc2x0 C. through 45xc2x0 C. Thermotherapy usually requires energy application to achieve a temperature above 45xc2x0 C. for the purposes of coagulating the target tissue. Tissue coagulation beneficially changes the density of the tissue. As the tissue shrinks, forms scars and is reabsorbed, the impingement of the enlarged tissues, such as an abnormal prostate, is substantially lessened.
The higher temperatures required by thermotherapy require delivery of larger amounts of energy to the target tissues. At the same time, it is important to protect non-target tissues from the high thermotherapy temperatures used in the treatment. Providing safe and effective thermotherapy, therefore, requires devices which have further capabilities compared to those which are suitable for hyperthermia.
Though devices and methods for treating benign prostatic hyperplasia have evolved dramatically in recent years, further progress is needed. As recently as 1983, medical textbooks recommended surgery for removing impinging prostatic tissues and four different surgical techniques were utilized. Suprapubic prostatectomy was a recommended method of removing the prostate tissue through an abdominal wound. Significant blood loss and the concomitant hazards of any major surgical procedure were possible with this approach.
Perineal prostatectomy was an alternatively recommended surgical procedure which involved gland removal through an incision in the perineum. Infection, incontinence, impotence or rectal injury were more likely with this method than with alternative surgical procedures.
Transurethral resection of the prostate gland has been another recommended method of treating benign prostatic hyperplasia. This method required inserting a rigid tube into the urethra. A loop of wire connected with electrical current was rotated in the tube to remove shavings of the prostate at the bladder orifice. In this way no incision was needed. However, strictures were more frequent and repeat operations were sometimes necessary.
The other recommended surgical technique for treatment of benign prostatic hyperplasia was retropubic prostatectomy. This required a lower abdominal incision through which the prostate gland was removed. Blood loss was more easily controlled with this method, but inflammation of the pubic bone was more likely.
With the above surgical techniques, the medical textbooks noted the vascularity of the hyperplastic prostate gland and the corresponding dangers of substantial blood loss and shock. Careful medical attention was necessary following these medical procedures.
The problems previously described led medical researchers to develop alternative methods for treating benign prostatic hyperplasia. Researchers began to incorporate heat sources in Foley catheters after discovering that enlarged mammalian tissues responded favorably to increased temperatures. Examples of devices directed to treatment of prostate tissue include U.S. Pat. No. 4,662,383 (Harada), U.S. Pat. No. 4,967,765 (Turner), U.S. Pat. No. 4,662,383 (Sogawa) and German Patent No. DE 2407559 C3 (Dreyer). Though these references disclose structures which embody improvements over the surgical techniques, significant problems still remain unsolved.
Recent research has indicated that enlarged prostate glands are most effectively treated with higher temperatures than previously thought. Complete utilization of this discovery has been tempered by difficulties in shielding rectal wall tissues and other non-target tissues. While shielding has been addressed in some hyperthermia prior art devices, the higher microwave energy field intensities associated with thermotherapy necessitate structures and methods having further capabilities beyond those suitable for hyperthermia which protect non-target tissues effectively. For example, the symmetrical devices disclosed in the above-referenced patents have generally produced relatively uniform cylindrical energy fields. Even at the lower microwave energy field intensities encountered in hyperthermia treatment, unacceptably high rectal wall temperatures have severely limited treatment periods and effectiveness. Accordingly, various new shielding methods and apparatus have been proposed recently to attempt to prevent all thermal energy from reaching non-target tissues such as the rectal wall.
In addition, efficient and selective cooling of the devices is rarely provided. This can increase patient discomfort and increases the likelihood of non-target tissue damage.
It is well known that different types of cells are differently susceptible to heat. For example, tumor cells can be killed at thermal doses that are lower than those doses necessary to destroy adjacent normal tissue. This knowledge can be used for therapy planning purpose, but this often leads to problems because the thermal fields are not sufficiently predictable in the body, because natural cooling mechanisms by blood perfusion cannot be modeled exactly. Thus, to kill all malignant cells with higher confidence, it is necessary to enhance the thermal dose either by raising the temperature or applying the thermal energy several times using a sequenced therapy approach.
Both enhancement strategies are known to have problems. On the one hand, the application of higher temperatures increases the risk of destroying non-target tissue structures. For example, in the treatment of prostate tissue for reducing the effect of a benign prostate hyperplasia (BPH) or for destroying prostate cancer tumors, an overheating of the rectal wall can lead to severe complications such as the creation of a fistula, and the overheating of the sphincter muscles can lead to incontinence.
If, on the other hand. a sequenced treatment mode is chosen, it has been found that the tissue builds up a protection by xe2x80x9cheat shock proteinsxe2x80x9d, which decrease the effect of subsequent conventional therapies dramatically. From in vitro tests, it is known that tissue, protected by heat shock proteins, can survive temperatures up to 20xc2x0 C. higher than non-protected tissue. These heat shock proteins have a life of 20 to 40 hours in vitro and possibly up to several days in vivo.
It is therefore an object of the invention to provide an improved apparatus and method suitable for thermotherapy or hyperthermia treatment.
It is a further object of the invention to provide an improved apparatus and method for thermotherapy treatment which provides substantially uniform irradiation of target tissues while effectively protecting non-target tissues from the temperatures of treatment.
It is another object of the invention to provide an improved thermotherapy device which includes a collimated irradiation of a target zone generally and selective cooling of non-target tissues.
It is still an additional object of the invention to provide an improved thermotherapy device which reduces tissue damage and discomfort by stimulating non-target tissues to generate heat shock proteins.
The present invention provides thermotherapy apparatus for protecting non-target tissue structures from unintended damage during thermotherapy treatment of target tissue located adjacent to the non-target tissue structures. Unlike prior art methods and apparatus which limit or prevent thermal energy from reaching non-target tissue, the present invention actually applies controlled thermal energy to non-target tissue. The thermotherapy apparatus comprises a thermotherapy probe preferably including an outer lumen, an inner lumen, and an energy source including an applicator portion that is adapted to be inserted into one of the lumens. A controller is operable in a first treatment mode for causing a heating medium to be supplied to one of the lumens for heating non-target tissue structures to be protected to a temperature that is sublethal to non-target tissue but is high enough to provoke the building of heat shock proteins in the non-target tissue. The controller is operable in a second treatment mode to control the energy source to provide heating of the target tissues to a second temperature that is high enough to kill a desired cell mass contained in the target tissue structure. The heat shock proteins substantially prevent destruction of the non-target tissue structures during the second treatment mode.
Further in accordance with the invention, there is provided a method for protecting non-target tissue structures of a patient""s body from unintended damage during thermotherapy treatment of target tissue located adjacent to the non-target tissue structures. The method includes the steps of: inserting into the patient""s body a thermotherapy probe including inner and outer lumens; pumping a heated liquid through the inserted thermotherapy probe for heating the non-target tissue structures in a first treatment mode to a first temperature that is sublethal to tissue structures but is high enough to provoke the building of heat shock proteins in the non-target tissue structures; positioning an applicator portion of an energy source in at least one of the lumens; and applying radiative energy from the energy source to the target tissue in a second treatment mode for heating the target tissue to a second temperature that is high enough to kill a desired cell mass contained in the target tissue.